Electric motor for a power tool

Abstract

An electric motor for use with a power tool includes a rotor having a body and a plurality of magnets coupled to the body, a stator having a plurality of electromagnetic coils surrounding the rotor, and an output shaft coupled to the rotor for rotation with the rotor. The output shaft defines a longitudinal axis about which the rotor rotates. The motor also includes a balancing member coupled to the output shaft for rotation with the rotor. The balancing member substantially balances a mass of the rotor about the longitudinal axis to reduce vibrations of the electric motor during use.

What is claimed is: 
     
         1 . An electric motor for the use with a power tool, the electric motor comprising:
 a rotor including a body and a plurality of magnets coupled to the body;   a stator including a plurality of electromagnetic coils surrounding the rotor;   an output shaft coupled to the rotor for rotation with the rotor, the output shaft defining a longitudinal axis about which the rotor rotates; and   a balancing member coupled to the output shaft for rotation with the rotor, the balancing member substantially balancing a mass of the rotor about the longitudinal axis to reduce vibrations of the electric motor during use.   
     
     
         2 . The motor of  claim 1 , further comprising a bearing supported on the output shaft, wherein the balancing member is located between the body of the rotor and the bearing. 
     
     
         3 . The motor of  claim 1 , further comprising a fan supported on the output shaft for rotation with the rotor. 
     
     
         4 . The motor of  claim 3 , wherein the balancing member is located adjacent a first face of the body of the rotor, and wherein the fan is located adjacent a second face of the body of the rotor opposite from the balancing member. 
     
     
         5 . The motor of  claim 3 , wherein the balancing member is supported on the output shaft adjacent the fan. 
     
     
         6 . The motor of  claim 1 , wherein the balancing member includes a bushing supported on the output shaft. 
     
     
         7 . The motor of  claim 6 , wherein the bushing includes a balancing feature of material removed from the bushing. 
     
     
         8 . The motor of  claim 6 , wherein the bushing defines a plurality of slots, and wherein the balancing member further includes an insert of balancing material positioned within one of the plurality of slots. 
     
     
         9 . The motor of  claim 8 , wherein the plurality of slots is formed in a face of the fan and arranged circumferentially about the longitudinal axis. 
     
     
         10 . The motor of  claim 1 , wherein the balancing member includes an overmold formed on the shaft, and wherein the overmold includes a radially-extending flange having a larger diameter than a remainder of the overmold. 
     
     
         11 . The motor of  claim 10 , wherein the overmold includes a balancing feature of material removed from the radially-extending flange. 
     
     
         12 . The motor of  claim 1 , wherein the balancing member includes a fan supported on the output shaft. 
     
     
         13 . The motor of  claim 12 , wherein the fan includes a plurality of fins extending from a first face of the fan and a balancing feature of material removed from a second face of the fan. 
     
     
         14 . The motor of  claim 12 , wherein the fan defines a plurality of slots, and wherein the balancing member further includes an insert of balancing material positioned within one of the plurality of slots. 
     
     
         15 . The motor of  claim 14 , wherein the plurality of slots is formed in a face of the fan and arranged circumferentially about the longitudinal axis. 
     
     
         16 . A power tool comprising:
 a housing;   a drive mechanism positioned within the housing; and   an electric motor positioned within the housing and operable to drive the drive mechanism, the motor including
 a rotor including a body and a plurality of magnets coupled to the body, 
 a stator including a plurality of electromagnetic coils surrounding the rotor, 
 an output shaft coupled to the rotor for rotation with the rotor and coupled to the drive mechanism to drive the drive mechanism, the output shaft defining a longitudinal axis about which the rotor rotates, and 
 a balancing member coupled to the output shaft for rotation with the rotor, the balancing member substantially balancing a mass of the rotor about the longitudinal axis to reduce vibrations of the electric motor during use. 
   
     
     
         17 . The power tool of  claim 16 , wherein the motor further includes a bearing supported on the output shaft, and wherein the balancing member is located between the body of the rotor and the bearing. 
     
     
         18 . The power tool of  claim 16 , wherein the motor further includes a fan supported on the output shaft for rotation with the rotor. 
     
     
         19 . The power tool of  claim 18 , wherein the balancing member is located adjacent a first face of the body of the rotor, and wherein the fan is located adjacent a second face of the body of the rotor opposite from the balancing member. 
     
     
         20 . The power tool of  claim 18 , wherein the balancing member is supported on the output shaft adjacent the fan. 
     
     
         21 . The power tool of  claim 16 , wherein the balancing member includes a bushing supported on the output shaft. 
     
     
         22 . The power tool of  claim 21 , wherein the bushing includes a balancing feature of material removed from the bushing. 
     
     
         23 . The power tool of  claim 21 , wherein the bushing defines a plurality of slots, and wherein the balancing member further includes an insert of balancing material positioned within one of the plurality of slots. 
     
     
         24 . The power tool of  claim 23 , wherein the plurality of slots is formed in a face of the bushing and arranged circumferentially about the longitudinal axis. 
     
     
         25 . The power tool of  claim 16 , wherein the balancing member includes an overmold formed on the shaft, and wherein the overmold includes a radially-extending flange having a larger diameter than a remainder of the overmold. 
     
     
         26 . The power tool of  claim 25 , wherein the overmold includes a balancing feature of material removed from the radially-extending flange. 
     
     
         27 . The power tool of  claim 16 , wherein the balancing member includes a fan supported on the output shaft. 
     
     
         28 . The power tool of  claim 27 , wherein the fan includes a plurality of fins extending from a first face of the fan and a balancing feature of material removed from a second face of the fan. 
     
     
         29 . The power tool of  claim 27 , wherein the fan defines a plurality of slots, and wherein the balancing member further includes an insert of balancing material positioned within one of the plurality of slots. 
     
     
         30 . The power tool of  claim 29 , wherein the plurality of slots is formed in a face of the fan and arranged circumferentially about the longitudinal axis.